Heat exchanger



FIG. 1 is a perspective view of a heat exchanger, showing my new design;

FIG. 2 is a side elevational view thereof;

FIG. 3 is a view, shown on an enlarged scale of one end thereof; and

FIG. 4 is a view, also shown on an enlarged scale, of the other endthereof.

The ornamental design for a heat exchanger, substantially as shown inthe accompanying drawings.